NAME
strncpy —
copy part of a string to
another
SYNOPSIS
#include
<string.h>
char *
strncpy(char
*dst, const char
*src, size_t
len);
DESCRIPTION
The
strncpy()
function copies not more than len characters from the
string src to dst. If
src is less than len characters
long, it appends ‘\0’ characters for
the rest of len. If the length of
src is greater than or equal to
len, dst will
not be NUL-terminated.
If the src and dst strings overlap, the behavior is undefined.
RETURN VALUES
The strncpy() function returns
dst.
EXAMPLES
The following sets chararray to “abc\0\0\0”:
(void)strncpy(chararray, "abc", 6);
The following sets chararray to
“abcdef” and does not NUL terminate
chararray because the length of the source string is
greater than or equal to the length parameter.
strncpy()
only NUL terminates
the destination string when the length of the source string is less than the
length parameter.
(void)strncpy(chararray, "abcdefgh", 6);
The following copies as many characters from
input to buf as will fit and NUL
terminates the result. Because strncpy() does
not guarantee to NUL terminate the string itself, it must
be done by hand.
char buf[BUFSIZ]; (void)strncpy(buf, input, sizeof(buf) - 1); buf[sizeof(buf) - 1] = '\0';
Note that strlcpy(3) is a better choice for this kind of operation. The equivalent using strlcpy(3) is simply:
(void)strlcpy(buf, input, sizeof(buf));
SEE ALSO
bcopy(3), memccpy(3), memcpy(3), memmove(3), strcat(3), strlcpy(3), strncat(3), wcscpy(3), wcslcpy(3)
STANDARDS
The strncpy() function conforms to
ANSI X3.159-1989
(“ANSI C89”).
HISTORY
The strncpy() function first appeared in
Version 7 AT&T UNIX.